azscott Posted October 29, 2009 Share Posted October 29, 2009 First off I don't have the powertrain manual that has the section on how to test the O2 with the DRB. However there are not alot of options in the DRB anyway. Second i just replaced the O2 sensor last week...symptoms are still the same...idle is erratic ranging from 600-1100 at times....it does not lope..rather it will either be one or the other. During idle, if I select sensors on the DRB and watch ALL of the sensors they all are acting correctly and within range ACCEPT the O2. The O2 sensor is cycling quickly between .5 volts (rich) and 4.5 volts ( lean)...and it does this erratically and rapidly. It even does this at higher sustained RPM's. I would assume this is the source of my issues as the O2 is a key sensor in the ECU deciding if it is in a rich or lean condition and if it is bouncing around rapidly and constantly it will or should cause what i am seeing. Of course the questions is....why is it cycling. I doubt it is the O2 sensor...although I have the old and can hook it up and see what it reads even without it being installed in the down pipe. My guess...and yours probably...freaking wiring problem. :fs1: What say ye all. scott Link to comment Share on other sites More sharing options...
Geonovast Posted October 29, 2009 Share Posted October 29, 2009 The Renix system does not listen to the O2 sensor unless it's warmed up. Is there any change between when it's cold and when it's at operating temp? Also.. I wouldn't cause an idle between 600 and 1100 a problem unless it affects it while you're trying to drive. It's probably just a sticking IAC. Link to comment Share on other sites More sharing options...
azscott Posted October 29, 2009 Author Share Posted October 29, 2009 Well if you read the Renix fuel injector manual it only ignores the O2 during crank mode. During warm up, Idle and so on it recieves input from the O2 sensor. The manual states...in warm up mode proper pulse width of the injector is determined by inputs from CTS, MAP, MAT, TPS ESS and O2. It certainly uses it for idle mode as that is clearly stated in the Renix manual. During idle mode it uses the O2 to establish proper air fuel ratio. Now wether or not it would cause any idle changes I don't know for sure...seems like it could....but would it...don't know. At the least it is not right. The ECU uses the O2 to ID wether it is lean or rich and if it is cycling then it should stand to reason the ECU would counter the wrong condition until the O2 cycled back to the correct condition. So in the least it has to be dickin with the ECU trying to maintain a proper Air/Fuel mixture. I would think? All the other sensors are within range and stable. The IAC was replaced at the same time as the O2 and neither made a difference. The IAC is getting the variable voltage from the ECU. As for difference when it is warm or cold...I will check. Are you asking about difference in idle speed or O2 sensor. As for idle..it does not matter too much what temp the engine is at...although mAYBE a little more twitchy when cold....actually may idle a little higher when warm..but hard to say...it seems to wonder at times. Other than that it runs great. Certainly accelerates fine and has never stalled. scott Link to comment Share on other sites More sharing options...
azscott Posted October 29, 2009 Author Share Posted October 29, 2009 ...the other possibility is that the O2 sensor and related wiring is fine....and it is sensing a rapid change in Air Fuel mixture. There is a kind of cycle that I can follow with the engine idle or sound. When it cycles back to Rich...you can hear the engine idle change. SO whatever is happening with the O2 sensor or levels is affecting the engine idle. Now I disconnected the O2 sensor and ran it like that for a minute...just to see what i would see. It did not change how the idle would change....the only thing i saw was the O2 sensor display would cycle between Open loop...closed loop. May be normal with a disconnected O2 although I would think it would lock out in one mode or the other....although I have no information to support that. scott Link to comment Share on other sites More sharing options...
Oizarod115 Posted October 30, 2009 Share Posted October 30, 2009 your o2 sensor is supposed to bounce back and forth rapidly, it goes Rich-lean-rich-lean-rich-lean. its not possible for the computer to keep the engine at a constant 14.7:1 ratio so instead it bounces back and forth and it averages out to the perfect ratio. thats what your truck is supposed to do. AND the renix does not use the o2 sensor before the engine gets out of warm up mode. if you read the sensor voltage in warm-up mode it will be 5v constant. Link to comment Share on other sites More sharing options...
Oizarod115 Posted October 30, 2009 Share Posted October 30, 2009 did you check to make sure the truck isn't cycling back and forth between loops wih the o2 sensor plugged up? it really sounds to me like your o2 sensor and related systems are operating correctly. normally if you don't see a rapid change in voltage then it isn't working. bookmark this link here http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm and then go to it and look at o2 sensor description and testing. Link to comment Share on other sites More sharing options...
azscott Posted October 30, 2009 Author Share Posted October 30, 2009 Yah...missed that link for the sesnors.....I have alot of stuff bookmarked but not that one...so it is working fine. Well thanks for pointing that out. 'Well...that is one piece of good news. The bummer is...what in the heck is casuing this stubborn idle problem. As it warms up the idle will climb from 600 to around 1050 when warm. Sort of the opposite of a cold engine I would think. usually they start high and will drop in idel RPM's. I am missing something simple I think. On the oether hand...it runs fine overall and maybe for a 20 year old engine...I should not worry... :D scott Link to comment Share on other sites More sharing options...
Oizarod115 Posted October 30, 2009 Share Posted October 30, 2009 Yah...missed that link for the sesnors.....I have alot of stuff bookmarked but not that one...so it is working fine. Well thanks for pointing that out. 'Well...that is one piece of good news. The bummer is...what in the heck is casuing this stubborn idle problem. As it warms up the idle will climb from 600 to around 1050 when warm. Sort of the opposite of a cold engine I would think. usually they start high and will drop in idel RPM's. I am missing something simple I think. On the oether hand...it runs fine overall and maybe for a 20 year old engine...I should not worry... :D scott well if thats all your problem is then IDFK buddy... my truck runs 7-800 or so cold, then when it gets warm it jumps to 1200 and then will settle (after several minutes) back to about 900-1000. i have NO idea why.. before i swapped out the intake and did all that crap it was opposite, it used to idle normal then get real low on occasion like 4-500 but never any lower. i think it's jst one of those renix things. :dunno: Link to comment Share on other sites More sharing options...
azscott Posted October 30, 2009 Author Share Posted October 30, 2009 ...yah I may just be getting too anal over it. In reality..it isn't an issue. It started out as one of those things I figured I would fix as I went along...try a little of this and a little of that....and then...somehow it became an obsession to figure it out. Since the DRB says everything is fine...I will be happy with that :cheers: Besides...I have a Peugot Tranny in it with a fuuny revese gear....I gots bigger things to worry about soon. :eek: Thanks guys Scott Link to comment Share on other sites More sharing options...
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